Formal use of 'pound(s) sterling'


I know that pounds sterling is very formal, but I need to know,
would six hundred and twenty thousand pounds sterling (writing in words) be correct?

(Tag question :slight_smile: )
Does the phrase To convert money in pound(?) sterling requires the plural form?
Or the singular form can be (also?) used – for example, this way:
‘To convert money in Pound Sterling’? (…into… ?)

I’m not Brit, so I cannot answer your PS questions, but I think it is convert into. In AmE, it would be convert into dollars.

I’d say convert/change into pounds, pounds sterling or sterling (‘sterling’ is an uncountable noun).

A million of pou… thanks!